Hundreds of years before Christopher Columbus, the Norse became the first Europeans to cross the Atlantic and settle in North America. This long-posited theory was finally proven in the 1960s, following an archeological expedition to the site of L’Anse aux Meadows on the northernmost tip of the island of Newfoundland. Until recently, the exact timing of the Viking settlement was only speculation, based on architectural remains, a few surviving artefacts and interpretations of Icelandic sagas written in the 1200s. But, as this video from Nature explains, using new carbon dating techniques, scientists at the University of Groningen in the Netherlands have found the exact year that a tree was felled by a Viking axe – 1021 CE. Further, this research also marks the earliest known point in history by which human migration had encircled the globe.